Such sources, e.g. sources of neutrons, are already known in the art, and a particular known type of neutron source is referred to as a “neutron tube”.
In this type of source, a source of ions is accelerated to a high energy to strike a target. Typically a Penning ion source is used. The target is a deuterium D or tritium T chemical embedded in a metal substrate, typically molybdenum or tungsten. The ions are accelerated to ca. 100 kV to impact onto the target, producing neutrons through the D-D or D-T reaction.
The D-T reaction produces 14.1 MeV neutrons.
The D-D reaction produces 2.45 MeV neutrons but with a cross-section around a hundred times lower than those generated by D-T reaction, i.e. a much lower flux of neutrons.
Therefore it is generally preferred to use a tritium-based target in order to obtain a high neutron flux.
The neutron yield is determined by the energy and current of the beam of accelerated ions, the amount of deuterium or tritium embedded inside the target, and the power dissipation on the target.
A limitation of such neutron tube is that the neutron production rate is generally limited to 10E4 to 10E5 neutrons from a D-T reaction in a 10 microsecond pulse.
The deuteron beam current ID of such source is generally in the order of less than 10 mA.
Moreover, access to tritium is highly restricted for security reasons, which is of course a problem for the commercial use of such source.
Furthermore, the tritium materials used in such source are radioactive, and thus require very specific security means.
In addition, such sources are also limited with respect to the duration of their pulses.
Indeed, for some applications it would be desirable to obtain ultra short pulses (i.e. pulses in the order of a few nanoseconds only)—and with sources as mentioned above it is generally not possible to obtain significant flux of particles in such an ultra short pulse.
It is known to generate such short pulses of neutrons using an accelerator. A system based on the D-Be reaction has been proposed. Deuterons from an ion source injector are accelerated in a cyclotron to 9 MeV and then directed onto a Be target to produce neutrons. Such system is however low current, large and complex.
It thus appears that the existing sources for producing pulsed beams (or more generally fluxes) of particles are associated to some limitations.
Moreover, the existing sources are exposed to an additional important limitation.
Indeed, the sources which operate on the basis of a pulsed voltage between two electrodes, in order to accelerate charged particles between the two electrodes, are exposed to a severe limitation imposed by the Child-Langmuir law.
This law limits the flux of charged particles between the electrodes, as a consequence of the accumulation of these charged particles between the electrodes.
This phenomenon is generally referred to as a “space charge” phenomenon. It constitutes a barrier which limits the operations of the existing sources.